Now showing items 1-11 of 11

    • Axisymmetric photonic structures with PT-symmetry 

      Ahmed Waseem, Waqas Waseem; Herrero Simon, Ramon; Botey Cumella, Muriel; Staliunas, Kestutis (International Society for Photo-Optical Instrumentation Engineers (SPIE), 2016)
      Conference report
      Open Access
      PT-symmetric structures in photonic crystals, combining refractive index and gain-loss modulations is becoming a research field with increasing interest due to the light directionality induced by these particular potentials. ...
    • Field concentration by Axisymmetric local PT-symmetry 

      Ahmed Waseem, Waqas Waseem; Botey Cumella, Muriel; Herrero Simon, Ramon; Staliunas, Kestutis (2016)
      Conference report
      Open Access
      We propose a new class of systems holding PT-symmetry only locally; the potential fulfills: U(r-r0)=U*(-r+r0 ) in a small neighborhood of any point r0, whereas on a global scale the system is only Parity symmetric: ...
    • Locally parity-time-symmetric and globally parity-symmetric systems 

      Ahmed Waseem, Waqas Waseem; Herrero Simon, Ramon; Botey Cumella, Muriel; Staliunas, Kestutis (2016-11-11)
      Article
      Open Access
      We introduce a class of systems holding parity-time (PT) symmetry locally, whereas being globally P symmetric. The potential, U = U(vertical bar r vertical bar), fulfills PT symmetry with respect to periodically distributed ...
    • PT-axisymmetric photonic nanostructures 

      Ahmed Waseem, Waqas Waseem; Botey Cumella, Muriel; Herrero Simon, Ramon; Staliunas, Kestutis (2016)
      Conference report
      Restricted access - publisher's policy
      Optical Parity-Time (PT-) symmetric systems support unusual properties. When the symmetric coupling between internal modes is broken the system becomes strongly unidirectional resulting in novel effects such as asymmetric ...
    • PT-axisymmetric VCSELs with linear central defect 

      Ahmed Waseem, Waqas Waseem; Botey Cumella, Muriel; Herrero Simon, Ramon; Staliunas, Kestutis (Institute of Electrical and Electronics Engineers (IEEE), 2017)
      Conference report
      Open Access
      Semiconductor Lasers and particularly Vertical-Cavity Surface-Emitting Lasers (VCSELs) are important laser sources used for many purposes. However, the applications of these lasers are mainly restricted by their strongly ...
    • PT-axisymmetry for extraordinary field confinement 

      Botey Cumella, Muriel; Ahmed Waseem, Waqas Waseem; Herrero Simon, Ramon; Staliunas, Kestutis (International Society for Photo-Optical Instrumentation Engineers (SPIE), 2017)
      Conference report
      Open Access
      Optical Parity-Time (PT-) symmetric systems support unusual properties when the symmetric coupling between internal modes is broken. We propose a new class of quasiperiodic PT-axisymmetric systems which lead to a simultaneous ...
    • Self-collimated beams in 2D complex periodic lattices from P- to PT-symmetry 

      Ahmed Waseem, Waqas Waseem; Botey Cumella, Muriel; Herrero Simon, Ramon; Staliunas, Kestutis (2017)
      Conference report
      Open Access
      We analyze self-collimation in two-dimensional periodic complex lattices. We consider P-symmetric and PT-symmetric complex lattices with different geometries, where the periodic modulations of both refractive index and ...
    • Self-collimation in 2D Complex P- and PT-symmetric systems 

      Botey Cumella, Muriel; Ahmed Waseem, Waqas Waseem; Herrero Simon, Ramon; Staliunas, Kestutis (2017)
      Conference report
      Open Access
      We predict the self-collimation phenomena (or equivalently, dynamical localization) in 2-dimensional P-symmetric and PT-symmetric complex potentials, with periodic modulations of both gain/loss and refractive index. ...
    • Self-collimation in PT -symmetric crystals 

      Ahmed Waseem, Waqas Waseem; Herrero Simon, Ramon; Botey Cumella, Muriel; Staliunas, Kestutis (AMER PHYSICAL SOC, 2017-05-10)
      Article
      Open Access
      We predict the self-collimation phenomena (or equivalently, dynamical localization) in two-dimensional PT-symmetric complex potentials, where the complex modulation is considered in the transverse, longitudinal, or ...
    • Stabilization of broad area semiconductor lasers 

      Kumar, Shubham; Ahmed Waseem, Waqas Waseem; Herrero Simon, Ramon; Botey Cumella, Muriel; Staliunas, Kestutis (International Society for Photo-Optical Instrumentation Engineers (SPIE), 2018)
      Conference report
      Restricted access - publisher's policy
      Broad Area Semiconductor edge-emitting lasers typically display self-focusing nonlinearity due to the refractive index dependence on the population inversion. It induces the homogeneous solution instability, multi-transverse ...
    • Stabilization of flat-mirror vertical-external-cavity surface-emitting lasers by spatiotemporal modulation of the pump profile 

      Ahmed Waseem, Waqas Waseem; Kumar, Shubham; Herrero Simon, Ramon; Botey Cumella, Muriel; Radziunas, Mindaugas; Staliunas, Kestutis (2015-10-20)
      Article
      Open Access
      We propose and demonstrate theoretically that vertical-external-cavity surface-emitting lasers (VECSELs) with external flat mirrors can be stabilized by applying a periodic spatiotemporal modulation of the pump current. ...